284 Biological Chemistry. 



output of nitrogen. It may be recalled that although the 

 greater part of the nitrogen is excreted in the urine in the 

 form of urea, not inappreciable quantities appear in other 

 compounds such as ammonia, uric acid, creatinine, etc. 

 The variation of the distribution of the nitrogen amongst 

 these different constituents has also been the subject of 

 many investigations. Attempts have been made to ascer- 

 tain how the distribution may be altered with varied 

 diets, and under pathological conditions, when metabolism 

 is abnormal. Amongst the most interesting of these 

 investigations are the ones dealing with the variation of 

 the uric acid output. It may be recalled that there is a 

 chemical relationship between uric acid and certain of the 

 hydrolysis products of nucleic acid, which is contained in 

 varying quantities in food (see p. 254), and as uric acid 

 plays an important part in the pathology of gout, such 

 researches have an immediate bearing on the suitability 

 of different diets for patients suffering from this disease, 

 for it is conceivable that part of the uric acid, at any rate, 

 may be derived from the diet. The literature is too 

 extensive, and the interpretation of the results obtained 

 too controversial, for it to be possible to give more than 

 a passing reference to the subject of uric acid excretion 

 in this place ; it affords, however, one more interesting 

 example of the utility of the investigations on the en 

 products of metabolism. 



So far no mention has been made of the chemi 

 mechanism by means of which the end products are pro- 

 duced from the initial products ; the discussion of this 

 subject is reserved for a later part of this chapter. It 

 may be stated here, however, that nitrogen apparently 

 undergoes scission from the proteins in the form of 

 ammonia, which is converted into urea by some method 

 in the liver. When the liver ceases to perform its normal 



Ulg 



